And I'm Robert Siegel. South Sudan is facing what the U.N. calls the world's worst food crisis. The man-made catastrophe in the young nation comes after months of fighting between rival political factions. Farmers haven't had time to plant or take care of their cattle. The Obama administration is tapping into emergency funds try to send aid and help stave off a famine. NPR's Michele Kelemen reports the U.S. is also stepping up the pressure on South Sudan's political leaders to put aside their differences and to do it soon.

MICHELE KELEMEN, BYLINE: On a visit the South sedan with her security council colleagues, the U.S. Ambassador to the United Nations, Samantha Power, issued this dire warning - three years after the country's independence, she says, South Sudan's leaders have pushed the country to the brink of becoming a failed state.

SAMANTHA POWER: This Security Council visit comes in a way as an emergency visit.

KELEMEN: A grave risk of famine looms over South Sudan, Power told reporters in the capital, Juba. She says, 50,000 children under the age of five are at risk of dying from malnutrition. The U.N. ambassador is warning all sides in the conflict that they could face sanctions if they continue to carry a out human rights violations and don't follow up on their commitments to stop the fighting.

POWER: We hear very worrying reports of more arms being brought into this country in order to set the stage for another battle - another set of battles - when the dry season commences. This is deeply alarming.

KELEMEN: Secretary of State John Kerry also issued a statement this week blasting South Sudan's President Salva Kiir and his rival Riek Mashar for missing deadlines in their peace talks while innocent people die. Kerry calls this an outrage. National Security Advisor Susan Rice says, South Sudan's political leaders must assume their responsibilities and put their peoples interests above their own. She says, the U.S. will offer another $180 million because, as her statement puts it, the scale of suffering is shocking. Oxfam America's Noah Gottschalk says, aid agencies in South Sudan are stretched thin.

NOAH GOTTSCHALK: Which is why we really need to see the violence stopping. We need all parties to really adopt zero tolerance for any targeting of aid workers, any obstructions to humanitarian access and to humanitarian aid being delivered to people who need it the most. And ultimately a political solution.

KELEMEN: The Humanitarian Policy Advisor for Oxfam says, this is a legacy issue - not just for South Sudan's political leaders but also for the U.S., which played a key role in helping the country become independent. Michelle Kelemen, NPR News, Washington. Transcript provided by NPR, Copyright NPR.